Male mallard’s bill gives females hint about sexual health

A new study conducted by researchers at the University of Oslo indicates that the color of a male mallard duck's bill may indicate how likely he is to pass on a sexually transmitted disease (STD). The scientists speculate that female ducks likely select their mate based in part on his bill hue, according to the BBC.

Male duck's sperm has the ability to destroy potentially harmful bacteria, such as E. coli. The researchers, who published their findings in the Journal of the Royla Society Biology Letters, found that the more colorful a duck's bill was, the more healthy his sperm proved to be.